The present invention relates to a tubular assembly that includes an internal plug. The internal plug (e.g., a solid plug of thermoplastic material) resides within at least a portion of a second tube, a portion of which resides within a first tube. Each of the first and second tubes have perforations that are aligned. The exterior surface of the plug includes cavities, at least some of which are aligned with the aligned perforations of the first and second tubes. Plastic material (e.g., thermoplastic material) is injected into the aligned cavities of the plug through the aligned perforations of the first and second tubes. The injected plastic material at least partially fills the aligned cavities, and embeds the edges of the aligned perforations therein, thus fixedly attaching the first tube, second tube and plug together.
Tubular frames are often used in support structures for the purpose of providing a combination of desirable physical properties, such as rigidity and stability, with a reduction in weight, relative to solid or more solid support structures. Support structures that make use of tubular frames include, for example, chairs (e.g., aircraft and automotive seats), wheel chairs, aircraft and automotive space frames, and motorcycle and bicycle frames.
Tubular frames typically include a plurality of tubular members that are assembled together by means including, for example, welding, brazing, soldering, crimping, gluing, and/or screwing the ends of the tubular members together. In addition, fasteners, such as rivets, may be used to join the ends of the tubular members together. The weakest point of a tubular frame is typically the point where the ends of the tubular members are connected together. When placed under load (e.g., cyclical loading): welds, brazings and solder points can crack; crimped and screwed tube ends can come undone; and adhesives and fasteners can fail, e.g., crack or shear.
It would be desirable to develop tubular assemblies that provide a combination of desirable physical properties, such as strength and rigidity, with light weight. In addition, it would be desirable that such newly developed tubular assemblies have tubular connection points that have improved resistance to failure under load.
U.S. Pat. No. 4,541,649 discloses a connection between at least one first tube and a second tube of a bicycle frame. The first tube of the connection of the ""649 patent has a flared terminus that is in engagement with the outer surface of the second tube. An injection-molded one-piece plastic casing fully surrounds the end portion of the first tube and fully surrounds a circumferential portion of the outer surface of the second tube in the zone of the engagement of the flared terminus of the first tube with the second tube.
U.S. Pat. Nos. 5,797,613 and 5,865,456 disclose a flex joint for a vehicle frame (e.g., a bicycle frame). The flex joint includes a flexible member of durable material (e.g., a metal plate), an encasement surrounding the flexible member (e.g., of nylon), and bores through ends of the flex joint. The ends of the flex joint of the ""613/""456 patent are disclosed as being inserted within a circular frame end having openings (e.g., openings 119). Shoulder pins are disclosed as being inserted into the bores of the flex joint through the openings in the circular frame ends.
U.S. Pat. No. 5,937,496 discloses plastic connection elements (having recesses) for tubular frames. The plastic connection elements of the ""496 patent are inserted within a hollow end of a tubular element, and the tubular element is deformed relative to the recesses of the plastic connection element, thus forming a tight fit there between.
U.S. Pat. No. 5,404,630 discloses a method of joining a frame tube to a lug. The method of the ""630 patent includes: forming through-holes in the lug; inserting a frame tube into the lug; deforming the frame tube such that outward projections are formed therefrom that engage the through-holes in the lug; placing a reinforcing tube within the frame tube; and deforming the reinforcing tube such that outward projections are formed therefrom that engage with the inside wall of the frame tube.
In accordance with the present invention, there is provided a tubular assembly comprising:
(a) a first tube having a plurality of perforations having edges;
(b) a second tube having a plurality of perforations having edges, a portion of said second tube residing within a portion of said first tube, and at least some of said perforations of said first and second tubes being aligned and together defining aligned perforations having edges; and
(c) a plug residing within at least a portion of said second tube, said plug having an exterior surface, said exterior surface having cavities therein, at least some of said cavities being aligned with said aligned perforations of said first and second tubes,
wherein said tubular assembly is prepared by a process comprising molding plastic material through at least some of said aligned perforations of said first and second tubes and into said aligned cavities within said plug, the edges of said aligned perforations being embedded in the plastic material extending therethrough, thereby fixedly attaching said first tube, said second tube and said plug together.
The features that characterize the present invention are pointed out with particularity in the claims, which are annexed to and form a part of this disclosure. These and other features of the invention, its operating advantages and the specific objects obtained by its use will be more fully understood from the following detailed description and accompanying drawings.
Unless otherwise indicated, all numbers or expressions, such as those expressing structural dimensions, process conditions, etc. used in the specification and claims are understood as modified in all instances by the term xe2x80x9cabout.xe2x80x9d